As is known, numerical-control milling machines currently used for producing gas-turbine blades comprise a supporting frame; a rocking worktable fixed to the supporting frame to oscillate about a horizontal axis of rotation over the worktable; and a work unit having a toolspindle movable in space to perform any desired milling operation.
The work unit normally comprises an upright fitted to the supporting frame to move in a horizontal direction parallel to the axis of rotation of the worktable; and a toolhead movable vertically, on command, along the upright, and which is normally equipped with an electrically operated horizontal spindle movable horizontally to and from the worktable in a direction parallel to its own axis of rotation.
The worktable normally comprises a rotary platform to which the work is fixed directly.
Milling machines of the above type also comprise a control unit for driving the various actuating devices on the machine to regulate in real time the tilt angle of the worktable, the angular position of the rotary platform, the position of the upright on the supporting frame, the position of the toolhead on the upright, and the position of the spindle with respect to the toolhead, so as to machine the work on the rotary platform fully automatically.
Milling machines of the above type have the major drawback of lacking versatility, and so only being used on a very small scale.